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Rupture of the cranial cruciate ligament (CCL) is a common problem and is the most common cause of a rear leg lameness in dogs. The cranial cruciate ligament in dogs is comparable to the anterior cruciate ligament (ACL) that is commonly injured in human athletes. Injury to this ligament in people is typically associated with some type of extreme trauma. In dogs, however, the ligament most typically ruptures during normal activities without any abnormal stress on the knee.
The knee is located on the back leg between the femur and the tibia. There are four ligaments present in the knee of dogs. These include the cranial and caudal cruciate ligaments and the medial and lateral collateral ligaments. Each ligament has a different function in stabilizing the knee joint of dogs. Ligaments are strong tissues that connect two bones. The cranial cruciate ligament is by far the most commonly damaged of all the knee structures. It is composed of two separate bands that function differently at various knee angles. Approximately 25 to 30% of dogs with cruciate ruptures will have tearing of only one band, which is referred to as a partial cruciate rupture. Most dogs however will have a complete tear involving the entire ligament.
The canine cranial cruciate ligament is thought to rupture because of continual stresses placed on the ligament during walking and running. This continual stress is primarily a result of the shape of the top of the tibia. The weight bearing portion of the top of the tibia is angled or sloped. During weight bearing movement, the pressure between the femur and tibia at this location causes the tibia to shift forward, producing repeated stress on the cranial cruciate ligament. This is believed to play a major role in rupture of the ligament in dogs.
Two other important structures in the dog knee are the medial and lateral menisci. These are C- shaped pieces of cartilage located inside the joint between the femur and tibia that help to stabilize the knee. The medial meniscus is commonly damaged in association with rupture of the cranial cruciate ligament in dogs. Meniscal tearing is painful and if a torn meniscus is identified at surgery it will be at least partially removed.
Medium to large breed dogs (e.g. retriever breed size) between the ages of 6 and 10 years are most frequently affected. However, dogs as young as 1 to 2 years old and of any size including toy and giant breeds can rupture their cranial cruciate ligament. Cats also can occasionally develop limping because of a ruptured cranial cruciate ligament.
Dogs will typically develop a sudden onset of non-weight bearing or toe-touching lameness. This will usually improve to some degree with a few weeks of rest. However, the lameness will typically recur with return to normal activity. Occasionally, an animal’s owner will identify an abnormal incident that caused the lameness such as falling off a deck or stepping in a hole. Most often however no incident is identified, and animals become lame while performing every day activities such as running and playing.
Nearly all dogs with tearing or damage to their cruciate ligament will have swelling or inflammation in the joint that is felt on the front part of their knee. Your veterinarian will most likely be able to feel this swelling. A definitive diagnosis of a complete cranial cruciate ligament rupture is based on palpable laxity or looseness of the affected knee. This laxity can be felt without sedation in some dogs, but others will need to be sedated in order to identify the instability. This looseness is called cranial drawer instability. The diagnosis of a partial cruciate ligament rupture is more difficult. Dogs with partial ligament tears will usually have swelling of their knee and pain when their knee is completely extended. A definitive diagnosis however is inevitably made during exploratory surgery of the knee. Dogs with longstanding complete or partial cruciate tears will commonly develop thickening on the inside of their knee, which is known as a medial buttress. They will also have arthritis visible on radiographs taken by your veterinarian. Radiographs are taken to make sure no other problems exist in the knee such as infection or cancer and to show how much arthritis is present. Occasionally, fluid will need to be collected from the joint if any question exists about the possibility of a joint infection, cancer or other knee conditions.
Yes, but other causes are very uncommon. Generally, the diagnosis is extremely straightforward. Other possible causes of rear leg limping include joint cancer, joint infection, trauma and auto-immune diseases. Some indication of one of these diseases will almost always be seen on a complete physical examination or radiographs of the affected knee. If anything about your dog’s limping does not “add up”, other tests such as blood work or joint fluid analysis will be recommended. This is fortunately not necessary in most dogs.
Approximately 40-50 % of dogs with one cranial cruciate ligament rupture will rupture the ligament on the other rear leg within two years of the first rupture.
Surgery is the treatment of choice for dogs with a cranial cruciate ligament rupture. Approximately 90% of dogs will return to near normal function within a few months of surgery. Several surgical options exist.
Some surgical procedures attempt to recreate the function of the cranial cruciate ligament with a prosthetic ligament, and are typically called a Lateral Suture. The prosthetic ligament runs in the same direction as the cranial cruciate ligament and therefore provides the same approximate function as the ligament. The biggest risk with this type of repair is that the prosthetic ligament can break or stretch causing recurrence of the instability and lameness.
The most popular type of surgery involves changing the shape of the top of the tibia to change the biomechanics of the knee – so that the cranial cruciate ligament is no longer needed for stabilization. These surgeries are called tibial osteotomies, and are typically recommended for any dog weighing more than 15-20 pounds. The two most commonly performed tibial osteotomies are the tibial plateau leveling osteotomy (TPLO) and the tibial tuberosity advancement (TTA). The cranial cruciate ligament is not replaced with these procedures, so there is no concern for tearing the ligament again in the future.
With any surgical procedure there is the potential for complications. Potential complications associated with any cruciate surgical procedure include problems with general anesthesia, incisional infection (5% of surgical sites), implant breakage (much more common with Lateral Suture technique), and failure to improve function (less than 10% of animals). Research has shown that a better outcome occurs more predictably with the tibial osteotomy procedures (TPLO, TTA) than with the Lateral Suture stabilization. Finally, less than 10% of dogs will have a significant complication.
Activity restriction: Your dog will need to have its activity controlled for 8 to 12 weeks following surgery. For the entire 8 to 12 weeks of recovery, your dog should avoid slippery surfaces (e.g. slick concrete, hardwood floors, tile, etc.) and long flights of stairs. He or she should be confined to a single room without access to jump on furniture. Your pet should not be allowed to play with other animals or people and should be on a short (i.e. less than 6 foot) leash and under your complete control at all times when outside for bathroom purposes.
Two situations pose a potential problem following surgery. One is continuous walking on the operated limb. This repeated stress increases the chances of a complication associated with healing of the incision and the deeper tissues (i.e. joint and bone) and predisposes the implants (i.e. bone plate and screws) to fail. The other is a sudden burst of energy causing extreme stress on the surgical site. This is the worst of all possible scenarios. It is therefore essential that your dog is on a leash under your complete control at all times while outside during the 8 to 12 weeks following surgery. If your dog has had a tibial osteotomy procedure (TPLO, TTA) he or she will only be able to return to normal activity after radiographs have confirmed bone healing. Healing is almost always complete by the end of 12 weeks.
Care of the incision: During the first 2 weeks after surgery, special attention needs to be paid to the surgical incision. You should watch for any type of cloudy or foul smelling drainage, opening of the incision, or excessive swelling. Swelling associated with the incision should progressively decrease over 2 weeks. To minimize swelling, the incision can be cold packed for 24 hours following returning home. The incision should then be hot packed 3 to 4 times daily for 5 more days. A protective Elizabethan (i.e. lampshade) collar will need to be worn by your dog at all times to prevent licking and checking of the incision until the time of suture removal.
Recheck examinations: Recheck examinations are generally scheduled for 2 weeks following surgery for suture removal and 8-10 weeks for final examination. If your dog has had a tibial osteotomy (TPLO, TTA), he or she will have radiographs taken at the final recheck visit.
Medications: We will provide you with instructions about medications to be taken following surgery. Generally, some type of pain medication will be administered for 10-14 days following surgery.
We recommend physical therapy in the post-operative period starting 4 to 5 days after surgery. The most simple form of physical therapy involves moving the operated knee through a full range of motion repeatedly for 10 to 15-minute sessions 3 to 4 times each day. This should continue for approximately 4 to 6 weeks following surgery. If you have any other questions about physical therapy, please consult with one of our surgeons or request a consult with Canine Rehabilitation of Nashville.
Cranial cruciate ligament rupture (CCLR) in dogs is similar to anterior cruciate ligament (ACL) rupture in people.
Approximately 30% of dogs with cruciate ruptures will have partial tears of the cranial cruciate ligaments.
Approximately 50% of the dogs with cruciate ruptures will tear the cranial cruciate ligament on their other leg within 2 years of the first tear.
Dogs with CCLR most often go to the veterinarian because of a sudden onset of non-weight bearing or toe-touching lameness on a rear limb.
Most of the time an owner will not see a reason for the sudden lameness.
A definitive diagnosis is made when your veterinarian feels abnormal looseness in the affected knee.
Surgery is recommended for all dogs with cranial cruciate ligament ruptures (CCLR)
The two most common surgeries are tibial plateau leveling osteotomy (TPLO) and tibial tuberosity advancement (TTA). These procedures are tibial osteotomies that involve changing the shape of the tibia rather than replacing the ligament.
Greater than 90% of dogs improve with surgery.
Potential surgical complications include:
problems with anesthesia
infection of the incision
failure to improve
Activity restriction is required for 8-12 weeks following surgery.